Planimeter-guide



J. J. KERR.

PLANIMETER GUIDE.

APPLICATION FILED MAR. 4 I920.

Patented Aug. 9, 1921.

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I I f lrmnm Nl T JOHN J'. KERR, OF ROCHESTER, MINNESOTA.

PLANIMETER-GUIDE.

Specification of Letters Patent.

Patented Aug. 9, 19291.

Application filed March 4, 1920. I Serial No. 363,304.

To all whom it may concern Be it known that I, JOHN J. KERR, a citizen of the United States, residing at Rochester, in the county of Olmsted and State of Minnesota, have invented certain new and useful Improvements in Planimeter-Guides; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention has for its object to provide a guide for use in connection with planimeters, and more particularly for guiding the tracing needle thereof over an area.

As is well known, the work in using a planimeter is very tedious and nervous, for the reason that the tracing needle must be held to closely follow the area line or else the reading of the planimeter will be inaccurate and it is often necessary to retrace an area line one or more times in order to secure a correct estimate. By the use of my guide, it is possible to trace an area line very quickly and accurately and with very little experience.

To the above end, the invention consists of the novel devices and combinations of devices hereinafter described and defined in the claim.

In the accompanying drawings, which illustrate the invention, like characters indicate like parts throughout the several views.

Referring to the drawings:

Figure 1 is a perspective View of a planimeter and the guide, as used in connection with the tracing needle in following an irregular area line; and

Fig. 2 is a perspective view of the guide.

The planimeter illustrated is indicated as an entirety by the numeral 3, with the exception of its tracing needle 4 and which needle 1s posltioned to trace an irregular area line 5.

The guide, as shown, is in the form of while the needle & is placed in the slot 7,.

at one end thereof, and moved longitudinally therethrough either to the end of the slot or the end of the section of the area line being traced. The needle 4 is then held stationary, and the plate 6 pivotally swung thereon, as indicated by broken lines in Fig. l, to bring the slots 7 into position over another portion of the area line to be traced. This process is continued until the entire area line 5 is traced by the needle 4..

It will thus be seen that the tracing needle l can be Inovedvery quickly through the slot 7 and the plate 6 pivotally swung on the needle I. and quickly positioned over another portion of the line to be traced.

What I claim is:

The combination with a planimeter having a tracing needle, of an elongated transparent plate having a longitudinally eX- tended slot of such width as to hold said needle against lateral movement, said needle also acting as a pivot on which said plate may be pivotally moved.

In testimony whereof I afiix my signature in presence of two witnesses.

JOHN J. KERR.

Witnesses 

